6)
a,b(c)+b,c(a)+c,a(b)=
(abc-ab)/90 +(bca-bc)/90+(cab-ca)/90=
(le reordonam convenabil)
=(abc-bc)/90 +(bca-ca)/90 +(cab-ab)/90=
a00/90+b00/90+c00/90
(100a+100b+100c)/90=(10/9)(a+b+c)
x=(10/9)(a+b+c)/(a+b+c)=10/9
9x=9*10/9=10, deci x=nr. natural
4)
1/12+(1/12)/2=1/12+1/24=3/24=1/8
5)
a)=1/59*(36/45+36/60+36/40)=
1/59*(4/5 +3/5 +9/10)=1/59*23/10=23/590
b)=28(1/4+(10/4-7/4)*8/7)=
28(1/4+3/4*8/7)=
28(1/4+6/7)=
28(31/28)=31
